Modern vehicles and industrial machinery rely on a number of recirculating fluids for effective operation. Oil for engine cooling, hydraulic oil, transmission fluids, lube oils and others are circulated through complex apparatus often with close tolerances. Machinery which relies on pumps, gears, servo-valves and other close-tolerance components is particularly sensitive to small particulate contamination in its service fluids. Effective filtration of these fluids can extend the effective life of apparatus and maintain operation at high levels of performance. Furthermore, to the extent fluids can be maintained free of contamination, the life of the fluid itself is extended saving costs due to fluid replacement and machinery down time. Another vital consideration is that many industrial fluids are difficult and costly to dispose of. To the extent old fluid can be cleaned the environmental problems of fluid waste disposal may be minimized.
One particularly effective type of fluid filter causes fluids to flow interstitially between layers of wound fibrous tissue. The fibrous tissue is typically wound on rolls of a particular depth. To minimize the resistance of the tissue for a given amount of tissue surface area, it is often desirable to provide a plurality of stacked tissue rolls. To ensure fluid flow exclusively through the tissue rolls, these filters are preferably provided with fluid collectors with peripheral flanges which engage with the tissue of an upper and lower tissue roll filter element to prevent the entrance of unfiltered fluid between the distinct rolls into the fluid collector--a problem known as channeling. Such a filter apparatus is disclosed in U.S. Pat. No. 4,017,400 to Schade, the disclosure of which is incorporated by reference herein.
A fluid collector serves to separate the fibrous tissue rolls from one another or from an adjacent surface and to at the same time provide unhindered passage for filtered fluid to leave the filter elements. Fluid collectors are known which are formed of injection molded plastic which have a plurality of alternating radial slots and ridges with the ridges serving to space the fibrous tissue roll elements from the collector and the slots serving to direct the filtered fluid into a central flow tube.
Because of the high pressures exerted on the fluid collector by the pressurized fluid and the filter elements, each filter collector must be sufficiently rigid to withstand these pressures. However, it is also highly desirable that the fluid collector present as little resistance as possible to the free flow of fluid. The less the total resistance to flow of the oil filter, including the collector, the greater the rate of fluid filtration allowable for a given fluid pressure.
What is needed is a fluid collector which rigidly spaces filter elements and yet which presents a minimal restriction to fluid flow.